I am thinking about free bsd. What do you think?
Unless you are expecting hundreds of thousands of hits per day, it doesn't matter what *nix flavor or what major distribution. they will generally all work the same, imho, the better question is, "what web server software should i use?" My answer to that is apache.
If you want a simple web server, then it seems you are making it harder than it should be. just throw a distro up and start apache.
Bah! I like FreeBSD and I like Linux, so it's really preference at this point since Apache runs both platforms. However, I really like Gentoo and so...